Transparencia De Referral Program 10 60 Credits
The invisible cost of various tools
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The simple mathematics of frequency
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Minimum viable stack
If you are thinking about referral the way most companies implement it, you are making a mistake even before the first deployment. I've seen dozens of referral programs come and go in the last five years, and the pattern is always the same: huge stack, security promises that don't stand up to a basic curl, and a "transparency" that hides more than it reveals. I'll show you exactly what needs to be in place, with real numbers and configurations that I've seen fail in production.
First, forget microservices for referral. I saw a Brazilian fintech spend 14 months building distributed architecture for a 10-60 credit program that never got off the ground. What works: A lean monolith with three essential tables. referrals (who referred, who was referred, timestamp, status), credits (balance, hold, expiration), and events (immutable, append-only, for auditing). Ordinary PostgreSQL, no Kafka no RabbitMQ no nothing. An event table that grows 2-3GB per month on average program, storage cost ~$15/month on AWS. Compare with the fintech stack: $4,200/month in infra before processing a single valid referral.
The API needs three endpoints. /referral-link generates the code, /track records the conversion, /balance shows the balance. Nothing more. I saw a company with 23 referral endpoints. Thirty-two. The attack surface grows exponentially with each additional route. In 10-60 credits program, each credit is potentially real money. Unnecessary endpoint is a vector of exploitation.
Security is not a feature, it is the feature. But not in the way they sell it. "End-to-end encryption" and "LGPD compliance" on a sales slide do not prevent me from finding, on average, 3.4 critical vulnerabilities in referral programs that I audit. The most common: non-existent or false rate limiting. I saw an implementation that returned 429 Too Many Requests but processed the request anyway. The status code was decorative. Check your code: is your rate limit read-only or does it actually block?
Referral hash needs to be cryptographically secure. It's not supposed to be "hard to guess", it's supposed to be impossible to predict. Sequential MD5 is a great option for account farming. Use HMAC-SHA256 with rotating salt, minimum 32 byte key, rotation every 90 days. Cost: zero. Implementation in any language: 15 lines. I saw companies use UUID v4 "because it's random" and think they were safe. UUID v4 has 122 bits of theoretical entropy, but poor implementations use predictable PRNG. In 2019, researchers at Cure53 explored exactly this across 12 different platforms.
Fraud detection is where transparency really matters. Rule that works in practice: score based on behavior, not identity. New user who converts within 30 seconds of creating an account? Score +40. Same IP indicating 8 accounts? Score +65. Same device fingerprint in 3+ indications? Score +80. Auto-Lock Threshold: 100. Human Review: 60-99. This isn't perfect, but it is auditable. Can you explain why someone was blocked. The opposite, which I often see, is black-box ML that no one understands, that rejects legitimate leads and the company can't explain why. In a credit program, "our algorithm detected an anomaly" is not acceptable. It's user money that you are holding without justification.
Referral logging needs to be paranoid in volume, not retention. Keep everything for a minimum of 18 months (LGPD is not the limiting factor here, it is the ability to investigate fraud that we discovered 9 months later). But do not log PII in plain text on the same systems. Separate: events with user_id hash, another system with real mapping, access via dual-control. Implementation cost: ~40 engineering hours. Cost of not implementing: in 2022, a delivery company had 2.3M referral credits drained in 72 hours because logs showed balance in plain text, and attacker with read-only access was able to map accumulation patterns.
The database needs two isolation levels. Balance reading cannot block credit writing. Use snapshot isolation at a minimum, repeatable read if you can afford the performance. In a 10-60 credit program, competition is not theoretical. Weekend promotion, 10 thousand users checking balance simultaneously, deadlock in SELECT ... FOR UPDATE is a real scenario that I have seen happen three times. Simple solution: balance cache with TTL of 30 seconds, invalidation due to credit event. Basic Redis, $20/month, eliminates 94% contention.
Webhook for credit notification is a common trap. "We send webhook to your system when credit is released." Beauty. What if it fails? What if your endpoint is outside? I saw implementations that tried once and gave up. Real transparency: queue with exponential retry, dead letter after 24 hours, failure dashboard. My pattern: 3 immediate retries, then backoff of 1h, 2h, 4h, 8h, then DLQ. Alert on any item in DLQ. This is basic operation, not enterprise.
Finally: what cannot be on the stack. You don't need blockchain for referral "immutability". PostgreSQL with WAL and continuous backup is more immutable than 90% of the blockchain implementations I've seen. You don't need a smart contract for "transparency". Smart contract with bug is transparent for everyone to see the exploitation in real time. You don't need "AI for credit optimization". Clear, documented, auditable business rules outperform opaque models in 100% of the cases I analyzed where the objective was security, not scale.
Minimum viable stack for referral of 10-60 credits: PostgreSQL, Redis, 3-endpoint API, HMAC hash, real rate limit, explainable fraud score, separate logging, webhook retry. All of this fits into $200/month infrastructure, implemented in 2-3 weeks by one person. What doesn't fit: another layer of abstraction that you don't control, another SaaS service that promises to "resolve referrals", another justification that "security is too complex to be transparent". It is not. It's just work that no one wants to do, so they sell it as if more is needed.
Demo: from chaos to ready post
Radar
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What no one tells you
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Practical checklist
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Practical setup
If you want to reproduce this setup, here is the starting point I used:
- Host: Tencent Cloud Invite & Earn — 2C2G 3-month free trial is a realistic starting point for most of what I describe above. Use the referral link to get the coupon.
- Tools mentioned in this post (all from my daily setup, no sponsorship): terminal, ssh, qdrant, nvidia nim, python, bun, sqlite.
- If this content helped you, consider buying me a coffee — that's how I justify spending weekends writing detailed posts like this.
- For tools and books referenced: Amazon Brazil (tag lermf-20) has the gear. Affiliate disclosure: I earn a small commission at no extra cost to you.
- Want to support the work and earn compute credits yourself? Tencent Cloud's referral program gives you 2 credits per free user and 10-60 credits per paid user — 1 credit = $1 voucher. Join via this link.
##FAQ
Q: Is this post sponsored?A: No. I pay for my own infrastructure and write based on what I actually use. Product mentions are for context, with a referral link that benefits both of us (you get a coupon, I get a small credit).
Q: What's the cheapest way to reproduce your setup?A: The Tencent Cloud Invite & Earn 2C2G 3-month free trial is enough to get started. After that, expect $5-15/month depending on usage.
Q: Do you have a code or template I can use?A: Posts like this usually link to a public repo or script in the practical section. If you want a guided setup, buy me a coffee and I'll prioritize writing the next tutorial.
Q: How do you keep this content independent?A: All posts are written on my own time, using tools I pay for. Affiliate links (Amazon tag lermf-20, Tencent referral) are disclosed and never the reason I write a post.
Q: Can I republish this content?A: With attribution and a link back to blog.lermf.org. For translation rights, contact via the BMC link.


